Performance Evaluation Study On Natural Gas Hydrate Inhibitor Used In Deepwater Drilling

With the decreasing onshore petroleum resources and the increasing offshore oil and gas proved reserves,China begins to attach great importance to the research on deepwater oil and gas drilling technology.Deepwater drilling faces many complicated technical challenges,for example,hydrate formation may occur in wellbore and multiphase pipeline under high pressure and low temperature conditions,and a large number of hydrate can block the upper annulus,the blowout preventer and kill line,it also can limit the motion behavior of drill string and have a bad effect on drilling fluid performance,which requires us to study the mechanism of hydrate and hydrate inhibitors in deep water drilling fluid in order to satisfy the requirements of the deepwater oil and gas exploitation.On the basis of literature research,this thesis studied the hydrate formation and decomposition as well as hydrate inhibitor performance in the aspects of macroscopic experiments and microscopic processes.The performance of the compounded solution with PVP and nicotinamide was tested using the new experimental apparatus of hydrate inhibitor evaluation,and then molecular dynamics simulation was used to investigate the microscopic processes of hydrate decomposition under the influence of those inhibitors in order to explore the mechanism of inhibitor molecular activated radicle.Finally,the performance of the new low temperature resistant kinetics YSY series was tested and the high subcooling degree resistance of the drilling fluids was improved by optimizing the original formula.The indoor appraisal test results indicate that the compounded solutions with PVP and nicotinamide have good hydrate inhibition performance,molecular simulation results show that the amide group is an active group in kinetic hydrate inhibitors,also prove that the steric hindrance effect of the polymer contain ring contributes to inhibit the nucleation rate of the crystals.Meanwhile,the new kinetics YSY series exhibit good hydrate inhibition performance under low temperature and the deepwater drilling fluid SDF series can delay hydrate formation over 330 min under-5℃,which can basically meet the needs of hydrate inhibition in the deepwater drilling industry.The experiment and simulation results lay the foundation of the deepwater drilling fluid field application test.